Heavy fighting erupted in South Sudan's capital Monday, hours after the U.N. Security Council called on leaders in the conflict-torn country to control their rival armed forces, and warned that ongoing attacks on civilians and U.N. facilities may constitute war crimes.

Gunfire and explosions rocked Juba as clashes broke out for a fifth day Monday after relative calm overnight.

'Urgent situation'

Japanese Ambassador Koro Bessho, the current president of the 15-member Security Council, spoke for the international body late Sunday in New York after more than three hours of emergency consultations about the crisis in Juba. He called conditions on the ground an "urgent situation," and said at least one Chinese peacekeeper had been killed and several Rwandan peacekeepers wounded.

South Sudan Second Vice President James Wani Igga (C), flanked by South Sudan President Salva Kiir (R) and First Vice President Riek Machar (L), addresses a news conference at the Presidential State House in Juba, South Sudan, July 8, 2016.

There were no official estimates of casualties by late Sunday, and it remained unclear at that time whether troops loyal to President Salva Kiir and those backing First Vice President Riek Machar would heed the U.N. demands. Local radio in the capital earlier reported as many as 276 dead in several days of violence, while a spokesman for Machar said at least 150 were killed with scores of others wounded.

The U.S. State Department has ordered the departure of all its non-emergency personnel from the U.S. embassy in Juba and has also warned U.S. citizens against traveling to South Sudan because of the ongoing fighting.

Power: Attacks are 'deplorable'

Samantha Power, the U.S. ambassador to the U.N., said the attacks in South Sudan are "deplorable" and that the "targeting of what are meant to be inviolable U.N. premises is totally outrageous and unacceptable and goes beyond even the savagery that we've seen over the life of this conflict."

Akshaya Kumar of Human Rights Watch said,"For too long, the U.N. Security Council has relied on the good will of South Sudan's leaders, neglected accountability and brandished empty threats of an arms embargo and individual sanctions." Kumar said that was a "losing strategy" that has "obviously failed."

"The council should make clear that attacks against civilians will not be tolerated and that U.N. peacekeepers will use the full force of their mandate and military capabilities to protect civilians under their care," said Kumar. "It should also finally impose an arms embargo, which could immediately ground the South Sudanese attack helicopters that are operated by foreign crews and constrain the ability of armed forces to target civilians going forward."

Ambassador Bessho also urged Kiir and Machar to "genuinely commit themselves to the full and immediate implementation of the [2015] peace agreement" that ended a devastating two-year civil war in the impoverished country.

Both leaders on Saturday issued joint calls for calm in the capital, but to little avail.

Displaced people, rebel base targeted

Witnesses said Sunday's fighting hit a U.N. encampment for displaced people for a second time in as many days, and also targeted a rebel base in the capital. Separately, a spokesman for Machar told Reuters that the vice president's residence had come under attack by Kiir loyalists. There was no immediate confirmation of that report.

Kiir, an ethnic Dinka, and Machar, a Nuer tribesman, fought each other in a two-year civil war that erupted after the president fired Machar in 2013. Machar has since been reinstated as part of the peace deal reached late last year that also led to the formation of a transitional unity government.

Neither leader, however, has yet offered a workable plan to integrate their forces.

The latest fighting in Africa's newest nation was the first major outbreak of violence since Machar was reappointed vice president in April.

The World Food Program says 4.8 million South Sudanese are facing severe food shortages this year, with parts of the impoverished country on the brink of famine. It also says fighting has driven 2.4 million residents from their homes, while hundreds of thousands of others have fled the country as refugees.

With the country's fragile economy in shambles, monitors predict as many as 1 million South Sudanese will have fled the country by the end of the year.